Method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform and work platform

ABSTRACT

The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

BACKGROUND OF THE INVENTION

The invention relates to a method of servicing the outer components of awind turbine such as the wind turbine blades and the tower with a workplatform and a work platform.

DESCRIPTION OF THE RELATED ART

Normally, wind turbines are erected in places in which the windconditions are advantageous e.g. in places with few obstacles blockingor altering the path of the wind. This means that the wind turbinesoften are positioned in more or less remote places with a poorinfrastructure such as in terms of road quality.

This creates some problems in relation to the necessary maintenance ofthe outer components of the wind turbines such as the wind turbineblades or the surface of the wind turbine tower. The magnitude of theproblems has accumulated significantly in recent years with theincreasing size of the wind turbines.

Previously, freestanding cranes or lifts have been used in connectionwith maintenance or reparation of the outer components of the windturbines. However, with the poor infrastructure, the transportation ofthe cranes or lifts to the erection places of the wind turbines issomewhat costly and time consuming.

In order to overcome the problem of transporting large and heavyequipment to the erection places different solutions have beensuggested.

One has been using persons lowering them selves down the side of thewind turbine tower or blades using ropes connected to the nacelle.However, the method naturally requires experts in climbing and issomewhat restricted in the work possibilities on the wind turbine and assuch not a feasible solution to the problems of maintenance orreparation of the outer components of the wind turbines.

Another has been the installation of a crane and a cable basketunderneath the nacelle of the wind turbine allowing the basket to belowered down the side of the wind turbine. However, the basket isdifficult to position correctly and difficult to work from due to itsunstable nature.

BRIEF SUMMARY OF THE INVENTION

The invention establishes a method and system for wind turbines withoutthe above-mentioned disadvantage.

The invention creates a method and system which allow one or moreworkers to be positioned at any adjacent position outside the windturbine such as near one of the wind turbine blades without involvingheavy equipment on the ground.

Further, the invention creates a method and system which allow safe andstable conditions for the workers.

The invention relates to a method of servicing the outer components of awind turbine such as the wind turbine blades and the tower with a workplatform, said method comprises the steps of:

-   positioning the work platform at the wind turbine tower,-   connecting the work platform to an upper part of the wind turbine    with at least one cable,-   raising the work platform with the cable and cable winding means to    a position of use, and-   holding the work platform to the side of the wind turbine tower with    holding means.

Hereby it is possible to establish a method that allows safe and stableconditions for one or more workers performing service on the outercomponents of a wind turbine such as the wind turbine blades and thetower.

In an aspect of the invention, said holding is established with at leasttwo sets of suction or vacuum cups, allowing an easily controllable butstill firm hold on the wind turbine tower.

In a further aspect of the invention, said holding is enhanced bypositioning said suction or vacuum cups on the ends of holding arms,said arms gripping around the exterior of the wind turbine tower. Herebyit is possible to establish a grip around the wind turbine tower, thegrip being advantageous in absorbing and withstanding any twists in thework platform.

In an even further aspect of the invention, said method furthercomprises the step of moving the work platform horizontally byextracting or retracting horizontal forcing means of the work platform.Hereby it is possible to position the work platform at any adjacentposition outside the wind turbine such as near one of the wind turbineblades.

In another aspect of the invention, the extracting or retracting isestablished telescopically by a number of arm sections in saidhorizontal forcing means. Hereby a preferred embodiment of the inventionis achieved that is simple to construct and control during use.

In a further aspect of the invention, cable guiding means angles thecable outwards in relation to the wind turbine tower from the startingpoint of the cable. Hereby an advantageous embodiment of the inventionis achieved.

In an even further aspect of the invention, said work platform is movedup or down by following and rolling with steering wheels of the platformon the surface of the wind turbine tower. Hereby a further advantageousembodiment of the invention is achieved.

The invention also relates to a work platform, said platform furthercomprises gripping means for holding the work platform to the tower.Hereby it is possible to establish an apparatus that allows safe andstable conditions for one or more workers performing service on theouter components of a wind turbine such as the wind turbine blades andthe tower.

In an aspect of the invention, said at least one cable comprises anumber of outer cables, said set including a main cable and one or moreadditional cables.

In a further aspect of the invention, said at least one cable furthercomprises an inner cable or cables.

The more than one cable may enhance the safety level of the workplatform.

In an aspect of the invention, said inner and outer cables are fixed tothe underside of the wind turbine nacelle at an inner and outeranchorage point in direction from the tower or to anchorage pointsinside the nacelle.

In an aspect of the invention, said gripping means comprises at leasttwo sets of suction or vacuum cups. With two or more sets of suction orvacuum cups it is possible to engage the wind turbine tower from morethan one side e.g. from opposite sides ensuring a more firm grip.However it shall be emphasized that the gripping means may beestablished with just one set of suction or vacuum cups engaging thetower in one position. The position is preferably in front of the workplatform ensuring a balance for the platform around the position.

The suction or vacuum cups may be used in connection with any type ofwind turbine tower such as towers made in metal or concrete.

In another aspect of the invention, said gripping means comprises atleast two sets of electromagnetic means. The electromagnetic means maybe one or more electromagnets in which the electric power supply for themagnets is controlled in order to hold on to/let go of the metal surfaceof the tower.

In a further aspect of the invention, said gripping means comprisesretaining means surrounding the wind turbine tower such as at least oneretaining belt or band. The retaining means surround the tower totallyor partly and are connected to the gripping means in which the grippingmeans may tighten or release the retaining means in order to hold thework platform at the position or to allow movement of the platform,respectively. The belt or band is preferably made in iron or an ironalloy. Further, the belt or band may be made in other materials such asa reinforced composite or woven material.

In another aspect of the invention, each of said at least two sets ofsuction or vacuum cups or electromagnetic means are flexibly mounted tothe end of a holding arm. With the flexible mounting of the cups orelectromagnetic means an advantageous possibility of adapting theholding arms to the more or less uneven surface of the wind turbinetower is achieved. Further, with the flexible mounting the inclinationof the tower does not affect the functionality of the cups orelectromagnetic means.

In a further aspect of the invention, said holding arm includes a basearm section, inner arm section and outer arm section. By the sectioningof the arms, an ability of angling the arms individually is achieved inorder to grip different sized wind turbine towers.

In an even further aspect of the invention, said inner arm section andouter arm section are pivotally connected and controlled by armactuating means in at least one direction. Hereby it is possible toadapt the arm sections to the inclination of the tower in questionregardless of the (small) size of the inclination.

In another aspect of the invention, said gripping means comprises one ormore steering wheels. With the steering wheels it is easy to verticallymove and roll the, work platform to a given position of use. Further thesteering wheels help controlling the path that the work platform followswhen it is moved up or down the surface of the wind turbine tower.

In an aspect of the invention, guard rails and a foundation define awork area of said platform. As modern wind turbines comprises a nacelleheight of more than 50 meters the workers need protection from fallingof the platform e.g. as a result of an unexpected wind gust or the like.

In an aspect of the invention, said gripping means and the foundationare connected through horizontal forcing means. With the ability offorcing or moving the work platform horizontally, it is possible to workwith different outer components of the wind turbine regardless of theirposition in relation to the wind turbine tower. Especially with modernwind turbines, in which the distance between the tower and the windturbine blades may be between 5 and 10 meters, the ability of moving thework platform horizontally is advantageous.

In an aspect of the invention, said horizontal forcing means includes anumber of horizontal forcing arms. With a number of arms, instead of onelong arm, the forcing means may be constructed with a smaller length.

In an aspect of the invention, said horizontal forcing arms areintegrated into each other as part of telescopic forcing means. With thetelescopic adaptation the necessary length may be obtained with a morecompact construction of the forcing means. Further, the telescopicforcing means ensures that the horizontal forcing of the work platformis achieved with a linear approach of the forcing means.

In an aspect of the invention, the side or sides of said platformincludes one or more indentations for receiving and docking one or morewind turbine blades. The receiving and docking of the blade in anindentation is especially important as the indentation defines an areathat at least partly surrounds the blade. The surrounding ensures thatthe blade may be retained from different positions e.g. retraining theleading or trailing edge together with both sides of the blade. Further,the workers may approach and get close to both sides of the bladewithout dangerously leaning out over the guide rails.

In a special embodiment the blade may enter the indentation andsubsequently be surrounded by the work platform wherein the surroundingis achieved by closing a pivotally connected section of the platformbehind the blade. The section preferably comprises the necessary guiderails allowing the workers to walk around the blade in its fullcircumference.

It shall be emphasised that the blade may be docked at any positionalong the sides of the work platform. The indentations are merelyadapted for a safer docking by allowing a better retaining of the blade.

In an aspect of the invention, said platform includes retaining meansfor retaining the wind turbine blade in one of said indentations. Theretaining means are important as they ensure that any movements in theblade is retained e.g. at a wind gust and thus protect the workers frompotential injuries during the work on the blade. As the blade ispositioned in an indentation the retaining means may attack fromopposite side against the surface of the blade ensuring a solid andcontinuing hold on the blade.

In an aspect of the invention, said retaining means includes one or moresuction or vacuum cups positioned on one or more rods as base part forthe retaining means. The hold by suction or vacuum cups ensures both thesolid and continuing hold of the blade and at the same time a gentlehold without any pressure marks on the blade.

In an aspect of the invention, said cable is controlled by cable guidingmeans e.g. by one or more cable guidance wheels in said means. Theabrasion of the cable may be avoided and thus ensuring the security ofthe worker on the platform.

In an aspect of the invention, said cable guiding means controls theangling of the cable. By controlling the angling of the cable, it ispossible to achieve different advantageous characteristics such asforcing the work platform against the tower. By forcing the platformagainst the tower the necessary strength of the gripping means may bereduced.

In an aspect of the invention, control means at least controls said armactuating means, horizontal forcing means, said one or more suction orvacuum pumps and/or said cable winding means.

In another aspect of the invention, said control means is connectedwired or wirelessly to and controlled by at least one remote control.Equipped with a remote control the worker may move more freely on theplatform and control the components of the platform more precisely andthus is both the flexibility and the security of the platform enhanced.

In a further aspect of the invention, said control means and auxiliarydevices are controlled with more than one remote control, said controlswork in a master and slave configuration. Hereby it is possible tocontrol components of the work platform or with the auxiliary devicescomponents of the wind turbine, such as the turning of the rotor, fromdifferent positions e.g. the work platform and the ground or thenacelle.

FIGURES

The invention will be described in the following with reference to thefigures in which

FIG. 1. illustrates a large modem wind turbine,

FIG. 2 a illustrates a work platform according to the invention movingupwards on the side of a wind turbine tower,

FIG. 2 b illustrates the work platform in a use situation,

FIG. 3 illustrates in more details the work platform on the side of awind turbine tower,

FIG. 4 illustrates the positioning of a wind turbine blade in relationto the work platform, the platform seen from below,

FIG. 5 illustrates in perspective the work platform according to apreferred embodiment of the invention,

FIG. 6 illustrates the connection between the wind turbine and the workplatform including a section hereof,

FIGS. 7 a and 7 b illustrate the work platform in which the pushingactuator means are in two different extraction positions,

FIGS. 8 a to 8 c illustrate different extraction positions of apreferred embodiment of the pushing actuator means,

FIGS. 9 a and 9 b illustrate a preferred embodiment of suction or vacuumcups according to the invention in front and rear views,

FIGS. 10 a and 10 b illustrate a preferred embodiment of cable windingmeans including a box holding the cable winding means,

FIG. 11 illustrates a flow diagram relating to a method of servicing theouter components of a wind turbine, and FIG. 12 illustrates anembodiment of a control system in connection with a work platformaccording to the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a modem wind turbine 1 with a tower 2 and a windturbine nacelle 3 positioned on top of the tower. The wind turbine rotor5, comprising three wind turbine blades, is connected to the nacellethrough the low speed shaft which extends out of the nacelle front.

As illustrated in the figure, wind beyond a certain level will activatethe rotor due to the lift induced on the blades and allow it to rotatein a perpendicular direction to the wind. The rotation movement isconverted to electric power, which is usually supplied to thetransmission grid as known by skilled persons within the area.

FIG. 2 a illustrates a work platform 6 according to the invention movingupwards on the side of a wind turbine tower in connection with amaintenance or reparation job on the wind turbine 1.

Further, it is illustrated that the wind turbine blades are pitched outof the wind (parallel with the wind) and not moving as the wind turbineis stopped during the job. The figure also illustrates that a worker ispositioned inside the work platform.

The work platform is connected to the wind turbine nacelle 3 with atleast one cable 7 in which the cables arrive at the nacelle from aposition underneath the nacelle. The work platform also comprisesgripping means 8 that substantially horizontal reaches out against theside of the wind turbine tower 2.

The cables 7 may be an integrated part of the wind turbine locatedinside the nacelle and lowered to the ground through openings in thebottom of the nacelle. Further, the cable may arrive together with thework platform 6 and be transported to the nacelle e.g. by a workercarrying the cable to the nacelle using the stairs inside the windturbine, securely fastening one end of the cable to the nacelle andlowering the other end down to the ground.

Another way would be to carry a thin rope to the nacelle and lower itdown to the ground, tie it to a cable end and drag the cable up to thenacelle on the outside of the wind turbine tower e.g. with the aid of alifter in the nacelle before securely fastening the cable to thenacelle.

After the cable has reached the ground or the nacelle, it is fastened tocable winding means of the work platform allowing the work platform tobe raised from the ground by winding the cable on the work platform.

However, in a further embodiment the cable winding means may bepositioned in the nacelle and the cable thus only firmly secured to thework platform;

The accumulators may, in another embodiment of the work platform, bereplaced or supplemented with a diesel generator positioned on the workplatform.

Finally, the figure illustrates that the work platform was transportedto the place of the wind turbine on a trailer connected to a truck 9e.g. the normal service truck of the company servicing wind turbines.The truck may include different tools or machinery needed in connectionwith the maintenance and reparation job. Further, the truck may be usedin supplying power to the necessary electric accumulators or aircontainers of the work platform e.g. during transportation by chargingthe accumulators from the generator of the truck, or the containers froma compressor.

FIG. 2 b illustrates the work platform in a use situation at the tip ofa wind turbine blade 5 in which the blade is ready for servicing by theworker on the platform.

In order to arrive at the position of FIG. 2 b from the position of FIG.2 a the work platform is lifted with the cable winding means whilesteering wheels of the gripping means 8 are forced against the windturbine tower allowing the work platform to roll over the surface of thetower during the displacement.

After arrival at the position of use the work platform is stillconnected to the nacelle through the cables 7 but is also connected tothe tower through the gripping means 8 which grippes the wind turbinetower 2 at least two positions (as will be explained in further detailsbelow).

The wind turbine blade is twisted to a position in which the worker hasaccess to the surface of the blade (the blade being in a positionsubstantially perpendicular to the wind at the figure). The wind turbineblade is also secured to the work platform in order to avoid anyunintended movement of the blade during the work process.

When the work is done at the position the gripping means 8 are releasedfrom the tower and the cable winding means lifts (and rolls) the workplatform to a new position in which the gripping means 8 are once againsecured to the tower. This may be repeated until the blade in its fulllength has been serviced.

Hereafter the other wind turbine blades may undergo the same procedure.The blade to undergo the procedure is rotated to meet the side of thework platform in which the movement may be achieved by turning the highspeed shaft linking the generator and the gear in the nacelle e.g. by anauxiliary device comprising an electric motor. Further, the movement maybe achieved by using the generator as an electric motor taking electricenergy from the public electric grid. Even further, a movement may beachieved by slightly and briefly pitching one or more blades into thewind.

FIG. 3 illustrates a preferred embodiment of the work platform 6according to the invention positioned on (and partly concealed by) thewind turbine tower 2.

The work platform is constructed with a foundation 18 surrounded byguard rails 13 in which the foundation and the guide rails defining awork area for the worker or workers.

The work platform further comprises cable guiding means 12 guiding twocables 7 a, 7 b to cable winding means 43. The cable winding means 43comprises motor and gearing means in which the gearing means has a highgearing ratio e.g. 1500 motor shaft rotations for each cable winding.

The work platform further comprises a box 10 at the side whereindifferent hydraulic and/or pneumatic components may be positioned (aswill be explained in connection with FIGS. 10 a and 10 b).

In a first embodiment the cable winding means 43 are positioned at thefoot of the cable guiding means 12 in which the winded cables 7 continuefreely down under the platform or even stay on the floor of theplatform. In another embodiment of the invention the cables may beaccumulated in a cable drum positioned inside the box 10 or anothersuitable place at the work platform.

The cable guiding means 12 comprises a number of guidance wheels thatdirect the cables 7 a, 7 b to the cable winding means 43 and protect thecable from abrasion. The cable guiding means is preferably positionedcentrally on the platform or the outer section of the platform inrelation to the tower.

In a situation in which the horizontal forcing means is fully retracted,the cables are vertical or preferably slightly angled to meet the cableguiding means. The angling of the cable is outwardly in relation to thewind turbine tower from its anchorage point of the wind turbine ensuringthat the work platform, regardless of the degree of extraction of thehorizontal forcing means, is forced against the tower. The angling isestablished with the positioning of the cable guiding means on the workplatform and the anchorage point.

In order to freely adapt the work platform to different anchorage pointsthe point of attack of the cable guiding means may be movedhorizontally. As the point of attack may be seen as the cable guidancewheels of the cable guiding means the movement of the attack point maybe achieved by moving the wheels. The moving may be established byhaving sets of openings for holding the shafts of the cable guidancewheels in which the sets are spaced apart.

The work platform also comprises different docking areas 11 a, 11 b fora wind turbine blade. The first docking areas 11 a are indentations onthe opposite side of the work platform in which the blade is allowed toenter one of the indentations with the front or trailing edge facing thework platform. When the blade is positioned in the indentation,retaining means from the work platform is forced against the sides ofthe blade keeping the blade fixed in relation to the work platform.

With indentations on opposite side of the work platform it is possibleto service wind turbine blades from both sides of the platform but thework platform may also work with just one first docking area 11 a. Thefirst docking areas and further docking areas are described in relationto FIG. 4.

The figure further illustrates the one (non-concealed) half of thegripping means 8 of the work platform. The gripping means includes anarm stretching out along the side of the wind turbine tower. The armfairly follows the surface of the wind turbine tower by comprising anumber of arm sections pivotally connected to each other. The grippingmeans 8 comprises a steering wheel 14 approximately at half-length ofthe arm, the wheel being forced against the surface of the tower 2.Further, at the end of the gripping means 8, holding means 15 ispositioned for holding onto the wind turbine tower 2.

FIG. 4 illustrates the positioning of a wind turbine blade in relationto the work platform, the platform seen from below.

The figure illustrates blades positioned in docking areas; on one sideof the work platform (solid line in the presentation a cross section ofthe blade) and on the opposite side (dotted line). The blades are bothdocked with the leading or trailing edge facing the side of the workplatform and the diametrical line of the blades being perpendicular tothe longitudinal direction of the platform. The figure also illustratesa situation in which the blade is docked parallel with the longitudinaldirection of the platform in a further indentation 11 b (dotted line).The blade may be retained in the further indentation by securing a straparound the blade and fixing the strap ends to the guide rail.

The figure further illustrates the retaining means being forced againstthe sides of the wind turbine blade. Each of the retaining meanscomprises a head and a base 16 a, 17 a; 16 b, 17 b, respectively. Theretaining means may simply be rubber heads or similar flexible memberson rods forced against the sides and fastened to the work platformensuring that the blade is retained. However, the retaining heads mayalso be suction or vacuum cups e.g. with connection to a vacuum pump.

FIG. 5 illustrates the preferred embodiment of the work platform in itsentirety and in perspective.

Especially the figure illustrates the gripping means 8 in its entiretywith both holding arms stretching out to grip the wind turbine tower attwo positions with the holding means 15 a, 15 b or to roll on thesurface of the tower with the two steering wheels 14 a, 14 b.

As it is also seen on the figure each arm of the gripping means 8comprises a base arm section 21 a, 21 b connected to an inner armsection 20 a, 20 b, said inner arm is connected to an outer arm section19 a, 19 b. The base arm sections are further connected to each otherand the work platform through a base part comprising horizontal forcingmeans 23.

The connection between the base and the inner arm sections is made rigidby a sidepiece. The connection between the inner and the outer armsections 19 a, 20 a; 19 b, 20 b is made variable by using a pivotalconnection and arm actuating means 22 a, 22 b, such as linear electric,hydraulic or pneumatic actuators, allowing the outer arm sections andespecially the holding means 15 a, 15 b to be moved closer to or furtheraway from each other.

Further, the figure illustrates another cable 7 c extending toward thework platform and entering at cable guidance means on the platform. Thecable guidance means directs the cable 7 c to the cable windingmechanism 44 at the centre of the gripping means 8.

Finally, the figure illustrates one of the retaining means 16 b, 17 bfor retaining a wind turbine blade in greater details.

The work platform, and especially the essential parts, such as thefoundation of the work platform 18, the horizontal forcing means 23and/or the gripping means 8, are preferably made in steel or steelalloys.

However, other metals may be used in the construction of the workplatform such as aluminium or aluminium alloys. Further differentcomposite materials may be used such as glass, aramid or carbon fibrematerials.

The cables connecting the work platform with the upper part of the windturbine are preferably steel wires. Ropes such as a nylon rope may alsobe used if the strength of the ropes is significant enough to hold theplatform including the workers.

FIG. 6 illustrates the connection between the wind turbine and the workplatform. The connection comprises several cables 7 that extend from thenacelle 3 to different positions on the work platform 6. The cables aredivided in inner or outer cables in which the terms “inner” and “outer”are to be understood as their position in relation to the surface of thewind turbine tower.

In a preferred embodiment the inner and outer cables are connected todifferent anchorage points on the underside of the nacelle. The pointsare positioned somewhere between the wind turbine tower 3 and the windturbine rotor 5 with the inner point closer to the tower than the outerpoint e.g. 0.2 and 1.2 meter from the tower, respectively.

The inner and outer cables extend to an inner and an outer position atthe work platform in which they are connected to separate cable windingmechanisms 43, 44, as explained in relation to FIGS. 3 and 4.

The enlarged section view further illustrates a preferred embodiment ofthe invention and especially the extension of the inner 7 c and outercables 7 a, 7 b from the underside of the nacelle.

The inner cable is illustrated as one cable 7 c that extend from aninner anchorage point to the inner position at the work platform withthe inner cable winding mechanism 44. The inner cable forms an angle αwith the underside of the nacelle.

The angle is preferably 90 degrees, the cable extends vertically, orless than 90 degrees, the cable extends outwardly in relation to thetower from the anchorage point.

The outer cables are illustrated as two cables 7 a, 7 b that extendsfrom an outer anchorage point 45 to the outer position at the workplatform. As explained above, the cable guiding means 12 is the outerposition at the work platform that guides the cables to the outer cablewinding mechanism 43. The outer cables form an angle β with theunderside of the nacelle. The angle is preferably 90 degrees, the cablesextend vertically, or less than 90 degrees, the cables extend outwardlyin relation to the tower from the anchorage point.

The anchorage points may be eyelets or similar preinstalled connectionpoints on the underside of the nacelle. In order to get to the anchoragepoints, the nacelle may comprise one or more small openings in the floorof the nacelle allowing a worker to position the cable at the anchoragepoint. Alternatively, the cables may enter the nacelle through openingsand be fixed to anchorage points inside the nacelle.

The function of the cables 7 a, 7 b, 7 c is the moving of the workplatform, i.e. lifting or lowering the work platform. The inner cableensures that the inner section of the work platform, including thegripping means 8, is correctly moved regardless of the conditions of thesurface that the steering wheels 14 meet on the wind turbine tower.

The outer cables ensure that the work platform as such is moved andespecially that the outer section of the work platform is moved. Theouter cables are divided into a main cable and one or more additionalcables for security reasons. The main cable may single-handed carry theweight of the work platform but in case of a cable break the additionalcables will maintain the work platform at the position. Further, thewinding speed of the cables are monitored by safety means ensuring thatthe winding speed does not exceed an upper limit such as 4 meters perminute. The safety limit ensures that the work platform is not handledat dangerously high speeds, e.g. by the worker, under normal conditionsor at failure situations such as a breakdown in a cable windingmechanism. The overspeed safety means is preferably electro/mechanicaldevices of a centrifugal or a magnetic motion type that slows down ortemporarily stops the work platform. The safety means may also stop thework platform in a situation of cable overwind or weight overload.

In order to keep the work platform horizontal or at least relativelyhorizontal, the platform comprises level indication means. The levelindication means may be a part of the control system, described inrelation with FIG. 12, and as such be part of the system generatingcontrol signals for the cable winding mechanisms ensuring the horizontalposition of the work platform. The level indication means may becombined with tension means monitoring the tension on each of thedifferent cables. Both at vertical and horizontal movement of the workplatform it is important to monitor and ensure the horizontal positionof the work platform, and it may be achieved by controlling the cablewinding mechanisms individually e.g. in order to achieve the horizontalposition and level the strain on the cables.

In a basic embodiment of the invention the number of cables is set tojust one cable wherein the cable is extended to an outer position of thework platform such as the cable guiding means 12.

Further, the cables may be fixed to the work platform and connected withcable winding mechanisms in the nacelle.

FIGS. 7 a and 7 b illustrate the work platform and especially thehorizontal forcing means 23 in two different positions.

FIG. 7 a illustrates the first position in which the horizontal forcingmeans 23 is fully retracted. The retraction of the horizontal forcingmeans 23 will position the work platform close to the wind turbinetower, e.g. allowing inspection and repair of the surface of the tower.Further, the position will be the normal position during trucktransportation of the work platform as well as the normal positionduring the initial lifting of the work platform along the wind turbinetower.

FIG. 7 b illustrates a second position in which the horizontal forcingmeans 23 is partly extracted.

As seen on the figure, the horizontal forcing means 23 includes a numberof horizontal forcing arms. The arms may preferably be four-sided tubesin which the tubes are telescopically integrated into each other. Thetubes may be extracted or retracted successively or individually bymeans of electric, hydraulic or pneumatic means.

The electric means may include one or more electric motors driving oneor more spindles. The hydraulic or pneumatic means may include a pistondriven by the hydraulic or pneumatic forces.

The extraction of the horizontal forcing means 23 will position the workplatform away from the wind turbine tower, e.g. allowing service of thesurface of the wind turbine blades.

As the distance between the wind turbine tower and the blades are quitesignificant at modem wind turbines, the horizontal forcing means 23should at full extraction be of a certain length such as between 5 and10 meters in order to be able to service any type of modern windturbine.

It should be understood that the term “horizontal forcing means” meansthat the forcing means preferably acts in a substantially horizontaldirection against the wind turbine tower. However, the forcing means mayin other embodiments be sloped to an angle significantly above or belowthe horizontal direction.

FIGS. 8 a to 8 c illustrate the structure of a preferred embodiment ofthe horizontal forcing means 23.

The forcing means comprises a fixed part 25 holding the extractable andretractable horizontal forcing arms 23 a, 23 b. The fixed part isnormally mounted underneath the foundation 18 of the work platform inits full length.

The dotted lines may be seen as the surface of the wind turbine tower orthe holding means 15 which the rest of the work platform is moved awayfrom with the extraction of the forcing means.

FIG. 8 a illustrates the structure in a retracted position for thehorizontal forcing means 23.

FIG. 8 b illustrates the structure in an extracted position for a firsthorizontal forcing arm 23 a of the horizontal forcing means 23.

FIG. 8 c illustrates the structure in an extracted position for a firstand second horizontal forcing arm 23 a, 23 b of the horizontal forcingmeans 23. The figure illustrates the horizontal forcing means 23 withboth arms in fully extracted positions. However, in further embodimentsthe number of arms may be more than two arms e.g. the use of three orfour arms of a shorter length than the present two

FIGS. 9 a and 9 b illustrate a preferred embodiment of the holding means15 for the wind turbine tower.

The holding means are preferably flexible mounted onto the ends of theouter arm sections 19 a, 19 b of the gripping means 8. The flexibilitymay be used in order to adapt the holding means to the slightly slopingsurface of the wind turbine tower 2.

Further, the holding means comprises two substantially oval holdingdevices (and rather long in an up-down direction) positioned next toeach other. However, the number of holding devices and their shapes maybe altered in order to meet different situations in which the presentshape is preferred in order to advantageously absorb vertical forces.

FIG. 9 a illustrates the holding means 15 seen perceptively from thefront. The holding means comprises an oval first and second suction orvacuum cup 27 a, 27 b.

The second cup 27 b includes a suction opening 28 in one end of the cupin which the opening is connected to a suction pump with tube means.Further, the second cup 27 b includes a connection opening 29 b in theother end of the cup. The opening is connected with a connection tube 30to a connection opening 29 a in the first suction or vacuum cup 27 a.The connection between the two suction or vacuum cups ensures that acommon pressure condition is established in the cups.

The suction or vacuum cups may include rubber rims or lips 32 in orderto retain the pressure condition inside the cups.

The two suction or vacuum cups are rigidly fastened to a connecting rod31. The connecting rod 31 may on the other hand be flexibly fastened tothe gripping means as mentioned above e.g. with some sort of a tip-uphinge.

FIG. 9 b illustrates the holding means 15 seen perceptively from theopposite side after being rotated half a turn.

The figure especially illustrates the outlet of the suction opening 28in which a tube, with connection to a suction pump, is to be mounted.

The two suction or vacuum cups on each side of the gripping means may beused in order to firmly engage the work platform to the wind turbinetower by applying a very low suction pressure or even vacuum inside thecups facing the tower surface. Together with the cable and the cablewinding means the work platform may be held in place by the grippingmeans.

FIGS. 10 a and 10 b illustrates the hydraulic and/or pneumatic meanspositioned in a box 34 at one side of the work platform.

FIG. 10 a illustrates the box 34 with ventilation opening 33 in a firstand second box door 35 a, 35 b. The doors allow full access to thehydraulic and/or pneumatic means inside the box.

FIG. 10 b illustrates some of the content in the box including needlevalves 36 controlling the hydraulic pump and tank 39 with the motor 38.The magnetic controlled needle valves 36 thus control the hydraulicfluid pumped to the horizontal forcing means and other hydraulicactuated means of the work platform. The box further comprises a vacuumpump 39 that supplies the different suction or vacuum cups. The box mayfurther comprise such means as electric accumulators and/or a dieselgenerator, a cable drum 37 in which the cables 7, 7 a, 7 b, 7 c areaccumulated and one or more containers comprising compressed air.

The air containers may be used as an energy source supplying some or allthe energy consuming components of the work platform wherein thepressure of the containers preferably are quite high such as up to 40bar.

In an embodiment of the invention, compressed air is used instead ofhydraulic pressure in retracting/extracting the horizontal forcingmeans. Further, the compressed air is used to drive the motors of thecable winding means in which the normally used electric motors arereplaced with pneumatic motors. Even further, the compressed air is usedto establish the necessary vacuum pressure for the suction or vacuumcups. The containers may be reloaded with compressed air from acompressor installed in the truck (as mentioned above) e.g. during thetransportation from one site of wind turbines to another. The remainingcomponents such as the control means may be supplied with electric powerfrom one or more electric accumulators.

The necessary energy may in another embodiment be supplied partly ortotally from the hydraulic system in which the hydraulic oil ispressurized with nitrogen supplied from nitrogen containers.

Even further, in an embodiment the different components may be suppliedwith electric power e.g. in order to drive the hydraulic and vacuumpumps in which the electric power is supplied from the utility grid. Anelectric cable may connect the work platform with a power outlet insidethe wind turbine e.g. a 400 or 24 V AC outlet. In another embodiment thecable connects the work platform with the generator of the truck whereinthe truck is kept running in order to supply the necessary electricpower without emptying the truck accumulators. The electric cable mayhang freely or be winded with a cable retraction mechanism.

From the box the necessary air and/or hydraulic tubes extend to thedifferent components that are supplied with suction or vacuum,pressurized air or hydraulic oil. Further, electric power cables maytransfer energy from electric accumulators, a diesel generator or theutility grid to any electric actuated, activated or controlledcomponents.

FIG. 11 illustrates a flow diagram relating to a method of servicing theouter components of a wind turbine.

The method may include some or all of the following steps offunctionality in servicing a wind turbine such as the wind turbinetower:

-   -   driving the truck with the work platform to the rural place of        the wind turbine or wind turbine park.    -   positioning the work platform in front of the wind turbine tower        with the steering wheels of the gripping means touching the        surface of the tower (step a of FIG. 11).    -   connecting a cable to the wind turbine nacelle as described        above (step b—part 1).    -   connection of the cable to the cable winding means of the work        platform in which the cable preferably is a bit angled in        relation to a vertical angle forcing the work platform slightly        against the tower (step b—part 2).    -   vertically moving the work platform and one or more workers to a        use position with the aid of the cable, the cable guiding means        and the cable winding means (step c).    -   securing the work platform to the wind turbine tower by        activating the suction or vacuum cups 15 of the gripping means        8.    -   work on the wind turbine tower e.g. checking and repainting        areas of the tower.    -   releasing the holding means and lowering the work platform to        the ground and positioning the work platform on a transportation        trailer (step f).    -   recharging the electric accumulators during transportation of        the work platform to new rural places of wind turbines.

In connection with the servicing of the wind turbine tower, a number ofchoices may be made including the decision regarding moving up or downwhen the work is finished in an area of the tower (step e). If the workis completed on the tower the work platform may be lowered to theground.

The method may include some or all of the following steps offunctionality in servicing a wind turbine such as the wind turbineblades:

-   -   driving the truck with the work platform to the rural place of        the wind turbine or wind turbine park.    -   positioning the work platform in front of the wind turbine tower        with the steering wheels of the gripping means touching the        surface of the tower (step a of FIG. 11).    -   connecting a cable to the wind turbine nacelle as described        above (step b—part 1).    -   connection of the cable to the cable winding means of the work        platform in which the cable preferably is a bit angled in        relation to a vertical angle forcing the work platform slightly        against the tower (step b—part 2).    -   vertically moving the work platform and one or more workers to a        use position with the aid of the cable, the cable guiding means        and the cable winding means (step c).    -   securing the work platform to the wind turbine tower by        activating the suction or vacuum cups 15 of the gripping means        8.    -   altering the horizontal position of the work platform by        extracting the horizontal forcing means in order to meet a wind        turbine blade (step g).    -   retaining the wind turbine blade at the work platform and        servicing the section of the blade within reach (step h).    -   work on the wind turbine blade e.g. checking or cleaning areas        of the blade.    -   altering the horizontal position of the work platform by        retracting the horizontal forcing means e.g. Allowing the wind        turbine blades to turn briefly before securing a new blade to        the work platform and performing the service process on this        blade (step 1). The distance of the turn of the rotor is        preferably approximately one third of a full turn in order to        position the new blade in front of the blade docking area.    -   moving the work platform to a new use position with the aid of        the cable and the cable winding means e.g. a higher position        (step c).    -   securing the work platform to the wind turbine tower by        activating the suction or vacuum cups 15 of the gripping means        8.    -   altering the horizontal position of the work platform by        extracting the horizontal forcing means in order to meet a wind        turbine blade (step g).    -   retaining the wind turbine blade at the work platform and        servicing the section of the blade within reach (step h). . . .        and so forth . . .    -   releasing the holding means and lowering the work platform to        the ground and positioning the work platform on a transportation        trailer (step m).    -   recharging the electric accumulators during transportation of        the work platform to new rural places of wind turbines.

In connection with the servicing of the wind turbine blades a number ofchoices may be made including the decision regarding moving up or downwhen the work is finished in an area of the blade (step i).

Even further, if the work is completed on one blade it may be decided tocontinue with servicing another blade (step j).

Even further, if the work is completed on all blades in question it maybe decided to lower the work platform to the ground (step k).

FIG. 12 illustrates an embodiment of a control system 40 in connectionwith a work platform according to the invention

In order to control and monitor the functionalities of the workplatform, it is necessary with a control system positioned on the workplatform e.g. inside the box containing cable winding means. The controlsystem is preferably a microprocessor-based system capable of receiving,transmitting, processing and storing signals. The control systemcomprises connections to the different means of the work platform thatneeds controlling or monitoring.

The connections of the work platform may be divided into differentgroups such as control cables 41 a-41 f ensuring that control signalsare transferred to control valves, switches and relays and sensor cablesreturning monitor signal to the control system, said signals concerningthe functionality of the different components.

The control cables may be cables 41 a controlling the functionality ofthe suction or vacuum cups 16 a, 16 b of the retaining means for a windturbine blade. Further cables 41 f may control the functionality of thesuction or vacuum cups 15 a, 15 b of the gripping means.

Other control cables 41 b, 41 d may control the functionality of thecable winding mechanisms 43, 44 for the inner and outer cables,respectively.

Even further, control cables 41 c may control the functionality of thehydraulic and/or pneumatic components of the box 10. More control cables(not illustrated on the figure) may control the status of the electricaccumulators, the air containers, the diesel generator or furthercomponents of the work platform.

The electric power cables may supply energy directly to mechanical meanssuch as electric actuators converting the electricity to a physicalchange in position of the actuator rod e.g. the arm actuating means inthe case they are electric driven. Further, the electricity may besupplied to pneumatic or hydraulic pumping means in which the pumpingmeans supply pneumatic or hydraulic power to different actuating meanssuch as the forcing means in the case they are pneumatic or hydraulicactuated. Even further, the suction or vacuum cups may be pneumaticsupplied from one or more vacuum pumps, said pumps preferably beingelectrically driven.

The control cables connect the control systems with control switches andrelays e.g. electric switches switching the electric power cables orhydraulic, pneumatic and vacuum pressure switches controlling the air oroil flow through the connection tubes.

The monitoring cables may direct different status signals of the workplatform to the control system such as the energy level of theaccumulators, the pressure levels etc.

If status signals indicate that the normal functionality of the workplatform is not possible, e.g. due to low energy level of electricaccumulators, the worker may choose to lower the work platform with theaid of a manually operated handle releasing the break of the cablewinding means. The break release is preferably only partly ensuring thatthe lowering speed of the work platform is below the abovementionedspeed limit. However, if the speed increases beyond the limit, the overspeed break will take effect and slow down or even stop the workplatform.

If it is possible the manual operation may be supplemented by theremaining electric energy of the accumulators e.g. Allowing the electriccontrol of some necessary components of the work platform such as thegripping means. Further, the control system may define a lower limit forthe accumulators wherein any normal functionality of the work platformis stopped if the limit is exceeded. After the limit has been exceeded,the work platform may preferably only be lowered.

The control system 40 may be wired or wirelessly connected to a remotecontrol 42. The wireless connection is established by usingelectromagnetic airwaves such as radio or infrared waves.

The remote control allows a worker to control the different componentsof the work platform e.g. movement of the horizontal forcing means, theactivation of the suction or vacuum cups or the raising/lowering of theplatform. Further, the remote control may comprise display means formonitoring the above-mentioned status signals of the differentcomponents or other signals such as the position of the horizontalforcing means. Even further, the control means or the remote control maycomprise sound generating means in order to inform the workers of thestatus of the work platform or one or more of the components of theplatform.

The remote control may be held by one of the workers positioned on thework platform, on the ground or even in the nacelle.

The remote control that controls the control system may also controldifferent components of the wind turbine. In an embodiment the remotecontrol controls the means that turns the rotor in connection with thechange of wind turbine blades at the work platform, e.g. theabove-mentioned auxiliary device comprising an electric motor. Further,the remote control can control any winding mechanism in the nacelle.

Even further, the remote controlling of the work platform may be dividedbetween several remote controls e.g. held by a worker on the workplatform and a worker on the ground or in the nacelle. The worker on theground or in the nacelle may remotely activate different components ofthe wind turbine while the worker on the platform controls the platformcomponents with his remote control. Preferably, the remote control heldby the worker on the platform overrules any other remote control e.g. ina master/slave remote control configuration.

The invention has been exemplified above with reference to specificexamples. However, it should be understood that the invention is notlimited to the particular examples described above but may be used inconnection with a wide variety of applications. Further, it should beunderstood that especially the work platform according to the inventionmay be designed in a multitude of varieties within the scope of theinvention as specified in the claims.

1. Method of servicing outer components of a wind turbine with a workplatform, said method comprising: positioning the work platform at awind turbine tower of said wind turbine; connecting the work platform toan upper part of the wind turbine with at least one cable; raising thework platform with the cable and a cable winder to a position of use;holding the work platform to a side of the wind turbine tower bydirectly gripping the tower with a holder on the work platform, saidholder comprising a gripper having at least one holding arm including abase arm section, an inner arm section, and an outer arm section; andmoving the work platform horizontally by extracting or retracting ahorizontal forcer of the work platform; said horizontal forcerpositioned between said gripper and said work platform and connectingsaid gripper with said work platform, said forcer comprising a number ofhorizontal forcing arms telescopically integrated into each other;wherein said inner arm section and said outer arm section are pivotallyconnected and controlled by a holding arm actuator in at least onedirection.
 2. Method according to claim 1, wherein said holding isestablished with at least two sets of suction or vacuum cups.
 3. Methodaccording to claim 1, wherein said holding is established with at leasttwo sets of electromagnets.
 4. Method according to claim 1, wherein saidholding is established with a retainer surrounding said wind turbinetower.
 5. Method according to claim 1, wherein said holding is enhancedby positioning suction or vacuum cups or electromagnets on the ends ofholding arms, said arms gripping around the exterior of the wind turbinetower.
 6. Method according to claim 1, wherein the extracting orretracting is established telescopically by said horizontal forcingarms.
 7. Method according to claim 1, wherein cable guide angles thecable outwards in relation to the wind turbine tower from the startingpoint of the cable.
 8. Method according to claim 1, wherein said workplatform is moved up or down by following and rolling with steeringwheels of the platform on a surface of the wind turbine tower.
 9. Workplatform for servicing outer components of a wind turbine, said platformcomprising: at least one cable connecting the work platform with anupper part of the wind turbine; a cable winder winding said at least onecable; a gripper for directly holding the work platform to a tower ofsaid wind turbine, said gripper comprising at least one holding armincluding a base arm section, an inner arm section, and an outer armsection; and a horizontal forcer positioned between said gripper andsaid work platform and connecting said gripper with said work platform,said forcer comprising a number of horizontal forcing armstelescopically integrated into each other; wherein said inner armsection and said outer arm section are pivotally connected andcontrolled by a holding arm actuator in at least one direction; andwherein said work platform is movable horizontally by extracting orretracting said horizontal forcer.
 10. Work platform according to claim9, wherein said at least one cable comprises a set of outer cables, saidset including a main cable and one or more additional cables.
 11. Workplatform according to claim 10, wherein said at least one cable furthercomprises an inner cable or cables.
 12. Work platform according to claim11, wherein said inner and outer cables are fixed to an underside of awind turbine nacelle at an inner and outer anchorage point in adirection from the tower or to anchorage points inside the nacelle. 13.Work platform according to claim 9, wherein said gripper comprises atleast two sets of suction or vacuum cups.
 14. Work platform according toclaim 9, wherein said gripper comprises at least two sets ofelectromagnets.
 15. Work platform according to claim 9, wherein saidgripper comprises a retainer surrounding the wind turbine tower. 16.Work platform according to claim 9, wherein said gripper comprises atleast two sets of suction or vacuum cups or electromagnets that areflexibly mounted to an end of said holding arm.
 17. Work platformaccording to claim 9, wherein said gripper comprises one or moresteering wheels.
 18. Work platform according to claim 9, wherein guardrails and a foundation define a work area of said platform.
 19. Workplatform according to claim 18, wherein said gripper and the foundationare connected through said horizontal forcer.
 20. Work platformaccording to claim 9, wherein a side or sides of said platform includesone or more indentations for receiving and docking one or more windturbine blades.
 21. Work platform according to claim 20, wherein saidplatform includes a retainer for retaining the wind turbine blade in oneof said indentations.
 22. Work platform according to claim 21, whereinsaid retainer includes one or more suction or vacuum cups positioned onone or more rods as a base part for the retainer.
 23. Work platformaccording to claim 9, wherein said at least one cable is controlled by acable guide.
 24. Work platform according to claim 23, wherein a positionof said cable guide controls an angling of the at least one cable. 25.Work platform according to claim 23, wherein said cable guide angles thecable outwards in relation to the wind turbine tower from an anchoragepoint of the cable.
 26. Work platform according to claim 9, wherein saidplatform includes a control mechanism for controlling said holding armactuator, said horizontal forcer, one or more suction or vacuum pumpsand/or said cable winder.
 27. Work platform according to claim 26,wherein said control mechanism is connected wired or wirelessly to andcontrolled by at least one remote control.
 28. Work platform accordingto claim 26, wherein said control mechanism, said arm actuator, saidhorizontal forcer, said one or more suction or vacuum pumps and/or saidcable winder are controlled with more than one remote control, saidcontrols working in a master and slave configuration.